Vapor degreasing apparatus



Nov. 1, 1955 T. F. MCALISTER 2,722,593

VAPOR DEGREASING APPARATUS Filed May 25, 1953 United States Patent VAPOR DEGREASING APPARATUS Terry F. McAlister, Chicago, Ill., assignor to Ben W. Sager, Highland Park, Ill.

Application May 25, 1953, Serial No. 357,267 14 Claims. (Cl. 21938) This invention relates to apparatus for degreasing obects, such as, for instance, metal objects, by subjecting them to vapors of liquid solvents.

Vapor degreasing is a process of cleaning oils and greases 01f of parts by using the vapor of the solvent rather than by immersing the parts in a liquid. The liquid solvent is placed in the bottom of a tank, where it is heated up to approximately 50 F., at which point the vapor rises in the tank, and the parts to be cleaned are suspended in it. The hot vapor immediately condenses on the relatively colder parts, pouring off as a stream of liquid solvent and taking the oils and grease with it.

It is important to note that this action constitutes a distillation process; thus the vapor that rises is vastly cleaner than the liquid solvent, doing a far more effective cleaning job than can be done by immersion or washing of parts. The impurities remain in the liquid in the bottom of the tank, and when the liquid becomes too dirty it is drained ofif and fresh solvent put in.

Some items which are most efficiently cleaned in a vapor degreaser are coated with oils and other foreign matter which will vaporize at the solvent temperature, and these vapors may flow out quite rapidly, disturbing the operator and those around the machine. To prevent this condition, the apparatus of the present invention is provided with an exhaust member that draws air across the upper open end of the degreaser tank and carries it to a place of exhaustion. The stream of air moving across the top of the degreasing tank carries with it such vapors or gases as may rise above the top of the degreasing tank, but does not tend to draw any of the solvent vapors out of the degreasing tank.

It is one of the objects of the present invention to provide a vapor degreaser which is portable in nature and wherein there is assurance that the vapors produced by the degreaser will remain within the degreaser tank. This is acomplished, in the preferred embodiment of the present invention, by providing a. degreaser tank which is adequately heat insulated for a major portion of its height and wherein the top portion of the degreaser is not heat insulated, so that the outside of the top portion of the tank is cooled by the surrounding air and thereby causes condensation of any vapors that may rise above the heat insulated portion of the tank. It is a still further object of the present invention to provide a degreaser wherein the solvent is electrically heated, with an automatic thermostatic control for turning off the heating current when the temperature within the tank, at an elevation approximately that of the terminus of the insulation, reaches a given value as determined by a thermostat located at that level within the tank.

It is a still further object of the present invention to provide a vapor degreasing apparatus of the above mentioned character with a heat controlled thermostat that can readily be changed to operate at difl'erent set values. This permits the operator to change from one solvent to another, where the solvents have different boiling points, by merely changing the temperature setting at which the ice thermostat causes opening of the electric circuit for the heater of the solvent. This arrangement also permits changing of the efliective height to which vapors will rise within the tank.

In accordance with the preferred operation, the solvent used is trichlorethylene or perchlorethylene, although it is to be understood that other solvents may be used.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

In the drawing:

Fig. 1 is a vertical section of a vapor degreasing tank and associated apparatus of the present invention;

Fig. 2 is a plan view of the degreasing apparatus of Fig. 1;

Fig. 3 is a horizontal sectional view taken along section line 33 of Fig. 1;

Fig. 4 is a perspective view of the thermostat shown in Fig. 1, showing the adjustability thereof; and

Fig. 5 is a schematic diagram including coils of the electric heater and the thermostat which controls the energization of the heater coils.

Referring to the drawings, the reference numeral 2 indicates, generally, a vapor degreasing tank in the form of a cylindrical steel drum in which the articles to be cleaned are suspended. The axis of the drum extends vertically and the top 3 thereof is open. The side walls of the tank are curved outwardly as at 6 to provide an annular bead or recess 7 within the tank. An opening 10 centered in the bottom 8 of the tank provides a space for a well or pan 12 which is sealed around the opening 10, as by welding or the like. The pan 12 is provided for holding a suitable liquid solvent, such as trichlorethylene or perchlorethylene, to be boiled by heat supplied by an electric heater 16 located beneath or within the pan 12. The vapor from such solvents is heavier than air and, as the solvent is evaporated, each new quantity of solvent vapor generated gradually pushes the vapor already formed above it upward in the tank. In this manner, the lower portion of the tank is filled with solvent vapor.

Communicating with the bottom of the pan 12 is a pipe 13 including a conventional valve 15through which the solvent in the pan 12 may be drained when desired, as for replacement.

The tank is secured to a wood platform 18 by channelshaped legs 20 that are secured to the bottom of the tank 2 in any suitable manner, such as by welding or riveting. The space between the bottom of the tank 2 and the platform 18 is filled with a suitable heat-insulating material 22. Casters 26, secured to the bottom of the platform 18, provide mobility to the apparatus.

A heat insulation jacket 28 forms a sleeve around the lower portion of the tank 2 and extends to a region a short distance from the top of the tank. The bottom of the jacket 28 rests on the platform 18 and may be fixedly secured to the tank 2 in any suitable manner as, for example, by screws 30. The upper portion 31 of the tank is uninsulated and is exposed to the air surrounding the tank for facilitating cooling and condensation of vapors as they approach the top of the tank.

A thermostatic electric switch 32, adjustable as to its temperature of operation as by an adjusting screw 33 (Fig. 4), is supported by any suitable means, in the recess 7 within the tank 2 just above the top of the insulating jacket 28. The thermostat 32 includes normally closed contacts which control the energization of the heater. The thermostat is adjusted so that its contacts will open at any desired value above or below the vaporization temperature of the solvent 14, but preferably below that temperature, for reasons which will be hereinafter explained.

Referring more specifically to Fig. 5, the electrical control circuit for the apparatus is shown. It includes a master on-off switch 34- which is connected across a 120 volt power line 36. The switch is closed to place the vapor degreasing apparatus into operation. Normally closed thermostat contacts 38 are in series with the energization coil of a relay 40. Upon closing of the switch 34, the relay 40 is energized. When the relay 40 is energized, the movable contact member 41 thereof is moved into position bridging a pair of stationary contacts 42. This establishes a circuit for the heating coils 44 of the heater 16. When the contacts 38 of the thermostat 32 become opened, the relay 40 becomes deenergized and at 42 it interrupts the flow of electricity to the heater 16. The heater is preferably one of low heat storage capacity so that upon opening of its electric circuit it stops supplying heat to the solvent within the pan 12 reasonably promptly.

The operation of the vapor degreasing apparatus is as follows:

When the master switch 34 is closed, the heater 16 is energized and brings the liquid solvent in the pan 12 to its boiling point. Further application of heat by the heater 16 causes vaporization of some of the liquid solvent. The resulting vapor is heavier than air and therefore stays at the bottom of the tank 2, gradually displacing the air above it as the volume of the vapors increases. The level of the top vapor rises until the vapor level reaches and even slightly exceeds the level of the thermostat 32. When the temperature in the region of the thermostat exceeds the setting of the thermostat, the thermostat operates to open the circuit of the electric heater 16. The heat stored in the heater 16 continues to vaporize a small amount of solvent even after the electric circuit to the heater has been opened, so that the vapor level rises slightly. As the temperature of the vapor in the region of the thermostat gradually drops below that at which the thermostat is set, the thermostat recloses the energizing circuit for the heater, thereby causing more of the solvent to be evaporated to raise the level of the vapor in the tank 2. Thus, the thermostat maintains the level of the vapor within the tank at the required amount. If the setting of the thermostat is slightly increased, the level to which the vapor rises before the heater is energized is increased, but in no event is the thermostat set at such a value as to cause the liquid solvent to be vaporized to the extent of causing the vapors to overflow the top of the tank. The height of the uninsulated heat conducting top portion of the tank 2 assures that vapors of the liquid solvent rising above the level of the thermostat will be condensed before they reach the top of the tank.

The thermostat 32 is preferably mounted within the recess 7 to escape injury by objects being lowered into the tank for degreasing.

It will thus be seen that both the thermostat 32 and the exposed cooled walls of the upper portion of the tank 2 cooperate to prevent escape of the vaporized solvent from within the tank 2. The thermostat 32 is preferably of the adjustable type so that the apparatus may be used with a variety of solvents having different boiling or vaporizing temperatures and so that the level of the vapors in the tank can be varied.

Objects to be cleaned or degreased are at room temperature at the time of introduction into the degreasing tank. They are suspended in the tank in any desired manner, either individually, depending upon the size or shape of the object, or in groups placed loosely within an open mesh metal basket. The vapor within the tank comes into intimate contact with the exposed surfaces of the objects that are suspended in the tank below the top of the vapor level within the tank. The vapor contacting the objects immediately condenses thereon and drips to the pan 12. The condensate of the trichlorethylene or perchlorethylene vapor dissolves surface grease and other contamination on the objects. By the time the temperature of the objects has risen to the temperature of the surrounding vapor the objects have been cleaned of coated grease and the like.

If the objects to be cleaned are of such a size that they extend into the upper portions of the tank 2, the thermostat 32 may be adjusted to control the height of the vapor within the tank so that vapor production will cease when the vapor level extends a distance above the thermostat 32 into the upper portion of the tank, and short of the opening in the top thereof.

Where the articles to be cleaned are coated with oils or other foreign matter which will vaporize at or below the temperature of the vaporized solvent, it is not uncommon for these vapors to flow out of the tank. To prevent the escape of these vapors into the air surrounding the tank, an exhaust member is provided which will immediately remove such noxious vapors without disturbing the degreasing vapors in the tank 2. To this end, a vertically extending skirt or hood 56 is removably supported above the upper edge of the tank 2 by any suitable means, as, for example, by means of a bifurcated support member 58 which rests on the rim of the top of the tank. The hood 56 extends around only a portion of the tank and has an opening 60 which communicates with an exhaust pipe 62 leading to a blower 64. The blower 64 draws a stream of air across the top of the tank 2, which carries undesirable vapors or gases into the opening 60 of the pipe 62 where it is carried to a suitable disposal location. The velocity of the stream of air so produced at the top of the tank 2 is sufficiently low that the heavy solvent vapors in the tank are not drawn upwardly thereby and wasted. However, any of the degreasing vapors that may rise to the top of the tank are carried away by the blower 64.

Although the preferred embodiment of the invention is here described in detail, the description thereof is intended to be illustrative rather than restrictive, as many details may be modified or changed without departing from the broader aspects of applicants invention.

I claim:

l. Vapor degreasing apparatus comprising an open top tank in which an article to be cleaned is to be placed, a heater adapted, when energized, to vaporize a solvent and cause the same to fill said tank to a predetermined level, and a thermostat supported above the bottom of and within said tank and coupled to said heater for controlling said level by controlling the energization of said heater, said thermostat being nestled within a recess formed in the walls of the tank.

2. Vapor degreasing apparatus comprising a tank in which an article to be cleaned is to be placed, an electric heater adapted, when energized, to vaporize a solvent and cause the same to fill said tank to a predetermined level, and means for controlling the vapor level comprising a thermostat mounted in the tank, said thermostat having contacts which when actuated shut ott the heater when the vapor has risen to a selected predetermined level, and means for selectively adjusting the vapor level in the tank by varying the thermostat setting to vary the temperature at which said contacts will be actuated.

3. An open-top tank adapted to be associated with a heater for evaporating a solvent which fills said tank to a predetermined level, the lower portion of said tank being heat insulated and the upper portion thereof being uninsulated and exposed and made of heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising above the heat-insulated portion of said tank.

4. A tank adapted to be associated with a heater for evaporating solvent which fills said tank to a predetermined level, the upper portion of said tank being uninsulated and exposed and made of a heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising to the upper portion of the tank,

heat insulation surrounding the tank from the bottom thereof up to the said exposed upper portion to inhibit vapor condensation on the tank wall below said exposed portion, and a thermostat Within said tank and located in the region of the top of said heat insulation, said thermostat being responsive to the temperature in the tank and adapted to control the energization of said heater so as to stabilize the level of the solvent vapor at said predetermined level.

5. A degreasing tank, an electric heater for evaporating a solvent which is to fill said tank to a predetermined level, the lower portion of said tank being heat insulated and the upper portion thereof being uninsulated and exposed and made of a heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising above the heat insulated portion of said tank, and a thermostat supported in said tank near the junction of said insulated and uninsulated tank portions, for controlling the vapor level in the tank, and means for adjusting the vapor level in the tank by varying the thermostat setting to vary the temperature at which said contacts Will be actuated.

6. Vapor degreasing apparatus comprising a tank, the tank being heat insulated from the bottom of the tank up to almost the very top thereof and a narrow band at the top of the tank being uninsulated and exposed and made of a heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising above the heat-insulated portion of said tank, and control means supported in said tank for controlling the vapor level in the tank.

7. Vapor degreasing apparatus comprising a tank in which an article to be cleaned is to be supported, the lower portion of said tank being heat insulated from the bottom of the tank up to almost the very top thereof and a narrow band at the top of the tank being uninsulated and exposed and made of a heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising above the heat-insulated portion of said tank, and a thermostat supported in the upper portion of said tank near the junction between the insulated and uninsulated portion of the tank for controlling the vapor level in the tank.

8. Vapor degreasing apparatus comprising a tank in which an article to be cleaned is to be supported, means including a heater for vaporizing a solvent and causing the vaporized solvent to fill said tank to a predetermined level, the lower portion of said tank being heat insulated and the upper portion thereof being uninsulated and exposed and made of a heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising above the heat-insulated portion of said tank, and a heater control means mounted on the tank in the region of said predetermined level to shut off said heater to terminate the vaporization of said solvent when said vapor has reached said predetermined level.

9. Vapor degreasing apparatus comprising a tank in which an article to be cleaned is to be supported, means including a heater for vaporizing a solvent and causing the vaporized solvent to fill said tank to a predetermined level, the lower portion of said tank being heat insulated and the upper portion thereof being uninsulated and exposed and made of a heat conductive material which is cooled by the surrounding air to condense the vaporized solvent rising above the heat-insulated portion of said tank, and a thermostat supported above the bottom of said tank, said thermostat having contacts adapted to shut off the heater to terminate the vaporization of said solvent when the vapor has reached said predetermined level.

10. In combination with an open-top vapor degreasing tank in which an article to be cleaned may be placed and immersed in a vaporized solvent, an exhaust means for drawing atmospheric air across the open top of said tank to carry away gaseous products which rise above the top of said tank.

ll. In combination with an open-top vapor degreasing tank in which an article to be cleaned may be placed and immersed in a vaporized solvent which is sufiiciently heavy to normally remain within said tank, an upstanding wall partially surrounding and extending above a portion of the periphery of the open top of said tank, an opening in said wall communicating with the space above said tank, and means communicating with the opening in said wall for drawing air across the open top of said tank to carry away noxious, gaseous products which escape from the top of said tank, and at a velocity which is sufiiciently slow that the vaporized solvent is not drawn-ofi from said tank.

12. In combination with an open-top tank adapted to be associated with a heater for evaporating a solvent which fills said tank to a predetermined level, an upstanding wall rimming the open top of said tank so that the opening into the tank is not appreciably obstructed, an opening in said wall communicating with the space above the tank, and means communicating with the opening in said wall for drawing air across the open top of said tank and into said wall opening to carry away noxious, gaseous products which escape from the top of said tank, and at a velocity which is sufficiently slow that the vaporized solvent is not drawn-off from said tank.

13. In combination with an open-top vapor degreasing tank in which an article to be cleaned may be placed and immersed in a vaporized solvent, a removable wall member extending about at least a portion of the periphery of the open top of said tank, an opening in said wall member communicating with the space above said tank, and means communicating with the opening in said wall member for drawing air across the open top of said tank and into said opening to carry away noxious, gaseous products which escape from the top of the tank.

14. In combination with an open-top vapor degreasing tank in which an article to be cleaned may be placed and immersed in a vaporized solvent, an upstanding wall surrounding at least a portion of the periphery of the open top of said tank, said wall forming a continuation of the tank walls and including a portion which extends inwardly a small amount so as not to appreciably obstruct the open top of the tank, an opening in said wall below the inwardly extending portion thereof communicating with the space above said tank, and means communicating with said wall opening for drawing air across the open top of said tank and through said wall opening to carry away noxious, gaseous products which escape from the top of said tank.

References Cited in the file of this patent UNITED STATES PATENTS 2,456,335 Skelly et al Dec. 14, 1948 2,475,809 Sullivan et al. July 12, 1949 2,510,859 Black et a1. June 6, 1950 

2. VAPOR DEGREASING APPARATUS COMPRSING A TANK IN WHICH AN ARTICLE TO BE CLEANED IS TO BE PLACED, AN ELECTRIC HEATER ADAPTED, WHEN ENERGIZED, TO VAPORIZE A SOLVENT AND CAUSE THE SAME TO FILL SAID TANK TO A PREDETERMINED LEVEL, AND MEANS FOR CONTROLLING THE VAPOR LEVEL COMPRISING A THERMOSTAT MOUNTED IN THE TANK, SAID THERMOSTAT HAVING CONTACTS WHICH WHEN ACTUATED SHUT OFF THE HEATER WHEN THE VAPOR HAS RISEN TO A SELECTED PREDETERMINED LEVEL, AND MEANS FOR SELECTIVELY ADJUSTING THE VAPOR LEVEL IN THE TANK BY VARYING THE THERMOSTAT SETTING TO VARY THE TEMPERATURE AT WHICH SAID CONTACTS WILL BE ACTUATED. 